Control apparatus for a rolling mill



Nov. 12, 1963 F. STRINGER 3,110,203

CONTROL APPARATUS FOR A ROLLING MILL Filed Aug. 13, 1957 3 Sheets-Sheet 1 Second Stand Control Apparatus Relay Device '62 60- Strip Strip Detector Detector;

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Roll Force "1 "*2 Space Between Rollers wnusssss: mvsmoe Loren E Stnnger @Mwkfi. BY (@914 a ATTORNEY Nov. 12, 1963 1.. F. STRINGER 3,110,203

CONTROL APPARATUS F OR A ROLLING MILL Filed Aug. 13, 1957 3 Sheets-Sheet 2 Fourth Stand Control Apparatus Reloy Device I i 64". 1 Strlp I Strip Detector J 46 Detector i l IO") 4- l 38 32 l 1 C? l 54 rl 24 m I I C34 30 m 3 ""11 42 Flg 37 3 36 A.C Voltage 39 Source Voltage Source Nov. 12, 1963 Filed Aug. 13, 1957 L. F. STRINGER CONTROL APPARATUS FOR A ROLLING MILL Motor 3 Sheets-Sheet 3 Control Control Control Control l 1 Compensation Compensation Compensohon *96 Device Device Device 98/ Fig.4.

United States Patent 3,119,293 CGNTRQL APPARATUS FOR A ROLLWG MELL Loren F. Stringer, Amherst Township, Erie County, N.Y., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa, a corporation of Pennsylvania Filed Aug. 13, 1957, Ser. No. 678,014 4 Claims. (Cl. 8035) The present invention relates, in general, to control apparatus for a device operative with a moving workpiece, and more particularly to control apparatus for a rolling mill operative with a moving workpiece or strip of metal, which apparatus is operative to detect the presence of the workpiece or the strip of metal and to compensate for operational changes due to movement of the workpiece, and more specifically to compensate for the loss of tension between adjacent stands of the rolling mill when the end of the metal strip leaves one of those stands.

It is an object of the present invention to provide improved control apparatus for a device operative with a moving workpiece and to compensate for the operational eiiect of the movement of said workpiece.

It is another object of the present invention to provide improved control apparatus for a device operative with a moving workpiece and to compensate for the movement of the workpiece regarding a predetermined operation of the device relative to that workpiece, for example, gauge or thickness control.

It is a different object to provide improved workpiece detection or sensing apparatus operative to respond to the presence and/or absence of a workpiece at a predetermined location in a workpiece travel path, and more specifically to provide apparatus including a temperature or infrared radiation responsive element in a unique snapaction control arrangement to provide a desired control signal for controlling the operation of a Workhandling device, such as, one stand of a rolling mill as a function of the position of a workpiece.

It is a further object to provide improved control apparatus for a rolling mill operative with a moving piece of material, which apparatus is responsive to the position of said piece of material to compensate for the effect of the movement of said piece of material relative to the operation of said rolling mill.

It is an additional object to provide improved gauge or thickness control apparatus for a strip rolling mill to compensate for the loss of tension in the strip resulting from a strip end leaving a particular stand of the mill, which apparatus is operative to control the operating speed of the next adjacent stand as required the control the delivery gauge or thickness of the strip from the rolling mill as desired.

These and other objects and advantages of the present invention will become apparent in view of the following description taken in conjunction with the drawings, wherein:

FIGURE 1 is a curve chart illustrating the operation of a rolling mill stand when the'back tension in the strip is lost due to the tail end of a strip leaving the preceding stand;

FIGS. 2A and 2B show a schematic diagram of the control apparatus in accordance with the teachings of the present invention;

FIG. 3 is a strip detector apparatus in accordance with the present invention; and

FIG. 4 is a schematic illustration of the present control apparatus.

In FIG. 1, H represents the incoming strip thickness, and 11 represents the desired output strip gauge with fixed front tension and back tension relative to a particular stand. I2 represents the resulting strip gauge with fixed Patented Nov. 12, 1963 front tension but zero back tension due to the strip end having left the preceding stand of the rolling mill. This will later be explained in greater detail relative to FIG. 4. It is desirable in accordance with the teachings of the present invention to return the strip thickness from 11 back to the desired output gauge or thickness h The output gauge from a stand of a rolling mill is a function of both the front tension T and the back tension T relative to that stand, and approximately is a function of the average applied tension as follows:

When the back tension T disappears relative to a given stand, due to the tail end of a strip leaving a preceding stand of the rolling mill, this increases the strip thickness or gaugeout of the next succeeding stand or said given stand to result in the delivery of off-gauge strip. Also the loss of back tension T tends to decrease the front tension T relative to that particular stand. Thusly, to return the strip to the desired gauge 11 if the front tension T is sufficiently increased, this will effect the desired return from the resulting undesired output gauge k when the back tension is absent to the desired strip gauge h. This increase in front tension may be efiected by increasing the speed of the next succeeding stand.

In FIGS. 2A and 213 there is shown a strip of material 10 operative with a first stand '12, a second stand 14 and a third stand 16 of a rolling mill which may include any desired number of stands. The first stand 12 is provided with a motor 18 for controlling the operating speed of the stand 12. The second stand 14 is provided with a motor 21' for controlling the operating speed of the second stand 14, and a third stand 16 is provided with a motor 22 operative to control the speed of the third stand. It should be here noted that any desired number of stands as desired may be provided in the rolling mill. A supply generator 24 is provided for the third stand motor 22 including a resistor 26 in series with the armature circuit of the motor 22. The generator 24 is provided with a field winding 28 operative with a conventional motor control amplifier 30, as well known to persons skilled in this art. A pilot generator 32 is operative with the mill motor 22 for providing a control signal as a function of the speed of the motor 22 to a control winding 34 of the amplifier device 30 for stabilizing the operation of the motor 22. This same control winding 34 is also energized by a droop speed control magnetic amplifier device 36 operative to control the speed droop of the motor 22. The droop magnetic amplifier 36 has a control winding 37 energized by a control signal from across a potentiometer 38 located in the rolling mill pulpit and manually adjusted by an operator for controlling the droop speed of the motor 22 as well known to persons skilled in this art. Also a reference potentiometer 39 is operative with a regulated voltage source 40 for providing a'speed reference for controlling the operation of the mill motor 22.

When the main circuit breaker 42 is closed, the control signal received from across the potentiometer device 38 is applied to the control winding '37 of the droop con trolling magnetic amplifier device 36 through the contact-or 44. A follow-up motor 52 is operative through the contactor 46 to control the position of the contact arm 54 on a potentiometer device as operative with a reference voltage source 58 such that the voltage drop e as sensed across the potentiometer device 56 and as determined by the position of the contact arm 54 through the operation of the follow-up motor 52 is substantially the same as the control signal 2 received from across the potentiometer device 38.

Strip detector devices 60, 62 and 64 are shown opera- .9 tive with respectively the first stand 12, the second stand 14 and the third stand 16 of the rolling mill, with the strip detector 62 being operative to provide a unit value signal to the control apparatus for the third stand 16 when the strip leaves the second stand l i and to provide a zero value control signal to the control apparatus for the third stand 16 While the strip 10 is still present within the second stand 14. The latter operation will be subsequently described in greater detail. Similarly, the

'strip detector device 64 is operative to provide a unit value signal when the strip 10 is not present within the third stand16 and to provide a zero value control signal when the strip 10 is present within the third stand 16. The strip detector devices are more fully described relative to the schematic showing of FIG. 3. a

When the strip 10 leaves the second stand 14, a unit value signal is provided by the strip detector device 62 to the input 66 of a switching transistor 68, within the control apparatus for the third stand 16, to switch the transistor 68 off which provides a base drive for the transistor 70 to switch the latter transistor 70 oil and switches the transistor 72 on.

It should be noted that switching is the most reliable mode of operation of transistors and the collector-emitter impedance is either high or low depending on whether no base drive or base drive is supplied.

In the operation of the transistors 76 and 72 as shown in FIG. 2B, the motor 52 varies the position of the contact arm 54 on the potentiometer 56 such that the control signal e obtained from the potentiometer device 56 operative with the constant potential source 58 is supplied to the control winding 37 of the droop controlling magnetic amplifier device 36 when the transistor 72 becomes conductive and the transistor 70 is no longer conductive. When the latter transistors 76 and 72 are switched, the contact 46 and the contact 44 are also opened by' suitable relay devices as will be explained relative to FIG. 3, such that the follow-up motor '52 is no longer operative to vary the position of the contact arm 54 and the control signal e then remains constant and equal to the droop control signal e from across the potentiometer device 38 which existed just before the switching occurred due to the strip detector 62 providing a unit value control signal to the input 66 of the transistor device 68 due to the strip 10 leaving the second stand 14. Thusly, the operative speed of the motor 22 is thereby clamped or held substantially constant by the potentiometer device 56 being inserted in the speed regulator reference circuit, including the control winding of the droop magnetic amplifier device 36, to thereby control the operative speed of the motor 22. By manual adjustment of the reference potentiometer 39 as may be desired a drop in motor speed adjustable by the pulpit operator may then be provided in the order of 3% or so.

The switching of: transistors 70 and 72, as above described, is controlled by a bistable Flip-Flop circuit consisting of transistor 68 and transistor 74 shown in FIG- URE 2B. When transistor 68 is oif, a base drive is supplied to transistor 70 and transistor 74 by the collector supply voltage of the transistor 68. Thusly, transistor 7 4 is switched on, and the base circuit of transistor 72 is effectively grounded such that transistor 72 is off. Thusly, with no input base drives to transistor 68 and transistor 74 a stable arrangement results. This arrangement is the desired one when the rolling mill is full, with the strip :10 being present within all of the stands and operating normally.

It should be here noted that the transistor devices 68 and 74 are each connected in a well known NOR circuit arrangement, such that each of these circuits does not have an output signal when any of its inputs is energized.

Referring to FIG. 3, the strip detector device is shown as including transistor 86, a 'phototransistor sensitive to infrared radiation and mounted in a special enclosure at the mill and directed down on the strip relative to a particular stand of the rolling mill from a location about 8 to 10 feet away from the strip. In the absence of hot steel strip present in the particular stand operative with a respective strip detector, radiation is not provided to the transistor 84 and the collector-emitter impedance of the transistor will be high such that the collector supply voltage is provided as a base drive for transistors 82 and 84. Transistors 82 and 86 provide a bistable Flip-Flop circuit. In the absence of a hot steel strip in the particular stand operative with a given strip detector, as shown in FIG. 3, the transistors 82 and 84 will be operative or conducting and the transistor 86 will be olf and not operative. If radiation is supplied by the presence of a hot steel strip, the transistor 86 will respond to this radiation and the base drives of transistors 82 and 84 are thereby removed and the base drive is applied to transistor 86 not only from transistor 84 but also from transistor 82. This provides a snap-action operation and makes the outputs at 8%; and 9t essentially equal to the collector supply voltage and independent of the intensity of the radiation source above a certain critical level. When strip is present in the particular rolling mill stand operative with a given strip detector, as shown in FIG. 3, the output will be provided with a zero value control signal and the output 88 will be provided with a unit value control signal. Since the output 90 has a unit value control signal when strip is not present in the rolling mill, it is used to drive the transistor 74 as shown in FIG. 2B in the control apparatus associated with the stand at the entrance of which the photosensitive transistor 8% is positioned as well as the transistor 68 in the compensator circuit associated with the next succeeding stand. The output 8-3 having a unit value con trol signal is used to control the operation of the relay device 89 operative with the contactors 44, 46 and 48 for the next stand operative. 88 for the strip detector device 62 operative with the second stand 14 controls the relay device 89 operative with contactors 44, 46 and 48 provided for the mill motor 22 of the third stand 16, as shown in FIGURES 2A and 2B.

Referring now to the schematic showing of FIG. 4, the strip 10 is operative with a rolling mill including N stands, with the strip 10 being movable between an entry reel 91 and a delivery reel 92 as well known to persons skilled in this particular art. The strip detectorv 60 operative with the first stand 12 provides a suitable control signal to the compensation device 96 operative with the motor 24 of the second stand 14. The strip detector device 62 for .the second stand 14 controls the compensation device 98 operative with the third stand, and so forth. Thusly, the strip detector provided for a particular stand of the rolling mill is operative to control the motor of the succeeding stand to vary the operative speed of the latter motor for the succeeding stand to compensate for the loss of back tension relative to the operation of said succeeding stand due to the strip leaving the preceding stand. No compensator device is provided for the first stand 12.

In the operation of the control apparatus in accordance with the present invention with therolling mill full of strip, the strip detectors for each stand provided with a detector are each providing a zero output control signal from the output 90 shown in FIGURE 3, such that, as shown in FIGS. 2A and 2B, in the compensation device for each stand the transistor 68 is On and the transistor 74 is Ofi for each stand so provided of the rolling mill. As the tail end of the strip 10 is about to pass out of stand 2 for example, the strip detector 62, as shown in FIGS. 2A and 2B, provides a base drive for the transistor 68 in the compensator device of the third stand 16. When this base drive is provided for the transistor 68, this switches Ofi the previously conducting transistor76 and switches On the transistor 72. In addition, the out- In other words, the output put control signal received from the output 94 of the strip detector 62 for the second stand 14 is utilized to open the contactor 45 and the contactor 44 and to close the contactor 48. Thus, during the time period that the tail end of the strip is traveling from the second stand 14 to the third stand 16, as shown in FIGS. 2A and 2B, the speed of the third stand is lowered .by an amount determined by the setting of the compensation potentiometer 56 and the front tension T between the third stand and the fourth stand is correspondingly increased.

When the tail end of the strip 10 is just about to leave the third stand 16, the strip detector 64 provides a base drive for the transistor 74 to switch on the transistor 70 as shown in FIG. 2B, and a base drive for the transistor in the compensation device for the next or fourth stand 17 of the rolling mill, corresponding to the transistor 68 in the compensator device for the third stand 16 as shown in FIG. 2B. Thusly, as the tail end of the strip 10 passes from stand to succeeding stand and out of the mill, the above action transfers from stand to stand to compensate for the otherwise occurring error in the output gauge or thickness of the strip.

With the rolling mill empty, the transistors 68 and 74 in all of the compensation circuits are Off. As the front end of a new strip enters the first stand 12 and then the second stand 14, and so forth, the strip detector for each respective stand switches the transistor 7% of the next succeeding stand On and holds the transistor 74 of the same stand compensator Off. This threading up procedure passes from stand to stand until the mill is again full and the transistor 70 in the compenastor circuit for each respective stands is On.

Thusly it is seen that in the operation of the present control apparatus, the speed of the succeeding stand relative to the stand from which the tail end of the strip 10 is about to leave is clamped to hold substantially continuity conditions of the next succeeding stand motor speed and to prevent the speed of the next succeeding stand to increase as would otherwise occur. This clamping of the speed of the next succeeding stand is accomplished by the potentiometer device 56 provided in the compensation device for each stand, such as shown in FIG. 2B relative to the third stand 16. In this regard, the control signal e from across the potentiometer device 56 follows and substantially is equal to the control signal e from across the potentiometer device 38 up to the time that the compensator device for a particular stand is switched. Then the control signal e from across the potentiometer device 56 is clamped and substituted for the otherwise varying control signal 2 from across the potentiometer device 38.

In the operation of the compensator circuit for the third stand 16, as shown in FIGS. 2A and 2B, the transistor 70 is normally conducting until the tail end of the strip It leaves the second stand 14. Then the transistor 78 is switched Oil, and the transistor 72 is switched On to provide a path for the now clamped second control signal e from across the potentiometer device 56. The control signal e is clamped by virtue of the opening of the contactor 46 to discontinue the operation of the follow-up motor 52 when the tail end of the strip 10 leaves the second stand 14.

In this regard, it should be noted that the first control signal e from across the potentiometer device 38 changes with the loading of the motor 22 for the third stand 16. The manual setting of the control arm of the potentiometer device 38 is determined by the operator in the mill stand pulpit and is made to give the desired operation of the rolling mill, but the control voltage e from across the potentiometer device 38 changes with the loading of the mill motor 22.

It should be further noted that when the tail end of the strip 10 leaves the third stand 16, it is desired to reset the compensation circuit, as shown in FIG. 2B, for the third stand 16 in preparation for receiving the next succeeding strip to pass through the rolling mil-l. This is accomplished by the control signal received through the strip detector device output 88 operative with the relay device 89, as shown in FIG. 3, and operative when energized to close the contactors 44 and 46 and open the cont-actor 4% for a given stand when the preceding stand is full and to open the contaotors 44 and 46 and close the contactor 48 when the tail end of the strip is eaving the preceding stand. Thus-1y, when the third stand 16 is empty, this provides a clear signal to reset the compensation circuit for the preceding or second stand 14.

It should be noted relative to the schematic showing of FIG. 4, that strip detectors are supplied for location at the entry sides of all but the last stand N of the rolling mill as the use of delivery tension imposed by the delivery reel 92 is preferably not utilized to compensate for loss of back tension T relative to the stand N when the tail end of the strip passes out of the preceding stand N-l.

Although the present invention has been described with a certain degree of particularity, it should be understood that the present disclosure has been made only by way of example and that numerous changes in the details of constrnction and the combination and arrangements of parts may be resorted to Without departing from the scope and the spirit of the present invention.

I claim as my invention:

1. In control apparatus for a workhandling member operative with a work travel path, the combination of a first control device responsive to infrared radiation from a workpiece at a predetermined location relative to said travel path and operative to provide a first control signal when a workpiece is present at said location, a second control device operatively connected to said first control device to be energized by said first control signal for providing a second control signal when said second control device is not energized by said first control signal, and a third control device having at least an On input connected to be energized by one of said first and second control signals, with said third control device being operative to provide a third control signal and connected to said work handling member for controlling a predetermined operation of said workhandlin member when said On input is not energized by said one control signal.

'2. In control apparatus for a workhandling member operative with a work travel path, the combination of a first control device responsive to the temperature of a workpiece at a predetermined location relative to said travel path and operative to provide a first control signal when a workpiece is present at said location, a second control device operatively connected to said first control device to be energized by said first control signal for providing a second control signal when said second control device is not energized by said first control signal, and a bistable Flip-Flop device having at least an On input connected to be energized by one of said first and second control signals, with said Flip-Flop device being operative to provide an output control signal and connected for controlling a predetermined operation of sad work handling member when said On input is not energized by said one of the first and second control signals.

3. In control apparatus for a workhandling member operative with a work travel path, the combination of a first NOR device responsive to infrared radiation i'rorn a workpiece at a predetermined location relative to said travel path and operative to provide a first control signal when a workpiece is present at said location, a second NOR device having an input operatively connected to said first control device to be energized by said firs-t control signal for providing a second control signal when the input of said second NOR device is not energized by said first control signal, and a third NOR device having at least an On input connected to be energized by one of said first and second control signals, with said third NOR device being operative to provide a third control signal and connected for controlling a predetermined op- 'eration of said workhandling member Whensaid On input is not energized by said one control signal.

4. In control apparatus for a workhandling member operative with a work travel path, the combination of a first NOR device responsive to infrared radiation from a workpiece at a predetermined location relative to said travel path and operative to provide a first control signal when a workpiece is present at said location, a second NOR device operatively connected to said first control device to be energized by said first control signal for providing a second control signal when said second control device is not energized by said first control signal, and a bistable third NOR device having at least an On input connected to be energized by one of said first and second control signals and an Oif input connected to be energized by the other of said first and second control signals, with said third NOR device being operative to provide a third control signal and operatively connected to said Work handling member for controlling a predetermined operation of said workhandling member when said On input is not energized by said one control signal and said OE input is energized by said other control signal.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN CONTROL APPARATUS FOR A WORKHANDLING MEMBER OPERATIVE WITH A WORK TRAVEL PATH, THE COMBINATION OF A FIRST CONTROL DEVICE RESPONSIVE TO INFRARED RADIATION FROM A WORKPIECE AT A PREDETERMINED LOCATION RELATIVE TO SAID TRAVEL PATH AND OPERATIVE TO PROVIDE A FIRST CONTROL SIGNAL WHEN A WORKPIECE IS PRESENT AT SAID LOCATION, A SECOND CONTROL DEVICE OPERATIVELY CONNECTED TO SAID FIRST CONTROL DEVICE TO BE ENERGIZED BY SAID FIRST CONTROL SIGNAL FOR PROVIDING A SECOND CONTROL SIGNAL WHEN SAID SECOND CONTROL DEVICE IS NOT ENERGIZED BY SAID FIRST CONTROL SIGNAL, AND A THIRD CONTROL DEVICE HAVING AT LEAST AN ON INPUT CONNECTED TO BE ENERGIZED BY ONE OF SAID FIRST AND SECOND CONTROL SIGNALS, WITH SAID THIRD CONTROL DEVICE BEING OPERATIVE TO PROVIDE A THIRD CONTROL SIGNAL AND CONNECTED TO SAID WORK HANDLING MEMBER FOR CONTROLLING A PREDE- 